To address moisture concerns in single-wythe CMU walls most masons use a through-wall flashing approach. Through-wall flashing is time-consuming, requires multiple block widths - which may have inconsistent colors, creates a poor flexural bond (because the bed joint of mortar is laid on top of the peel and stick flashing) and is susceptible to concave surfaces which won't drain. Through-wall flashing is an old school approach that takes a lot of work - but doesn't work all that well.

Single-Wythe Through Wall Flashing Gets an Upgrade

The MTI Slope-To-Drain tool creates a 1/4" per foot slope to drain on the bond-beam grout. The peel and stick flashing is installed on the grout, with space left on the edges for the bed joint of mortar. Roll out MTI Cavity Weep on the flashing, and then lay the bed joint of mortar and a the next row of block. Score and snap off the Cavity Weep, and then tool the joint for a finished look.

]]>Better Brick Mortar Control is Better Moisture Controlhttps://www.mtidry.com/blog/brick-mortar-control/
Tue, 06 Dec 2016 20:42:31 +0000https://www.mtidry.com/blog/?p=39Cavity masonry construction is rooted in a theory of moisture control by draining water to the exterior. Mortar still clogs the cavity, just higher up. Drainage and ventilation are limited.1 Mortar Deflection Device Pitfalls Mortar deflection devices claim to hold mortar above the weeps, and most accomplish this. However, the problem is just moved up …

Cavity masonry construction is rooted in a theory of moisture control by draining water to the exterior.

Mortar still clogs the cavity, just higher up. Drainage and ventilation are limited.1

Mortar Deflection Device Pitfalls

Mortar deflection devices claim to hold mortar above the weeps, and most accomplish this. However, the problem is just moved up the wall. The mortar dams up the cavity, limiting drainage and ventilation. Cavity masonry construction must not simply hold the mortar above the weeps but rather ensure a clear moisture drainage pathway behind the entire veneer.

Cavity masonry construction must not simply hold the mortar above the weeps but rather ensure a clear moisture drainage pathway behind the entire veneer. Mortar that bridges the masonry cavity can lead to moisture transfer and degradation of materials.

MTI's Mortar Control System addresses these concerns and provides proven protection for wall systems.

Mortar Control with Sure Cavity™ and Cavity Weep™

MTI’s Mortar Control System features two components: the Sure Cavity Drainage Plane and the Cavity Weep weep system. Sure Cavity features “True Channel” drainage technology with clear, rigid channels that quickly and effectively drain moisture and ventilate the cavity. The Sure Cavity ensures ventilation across the entire backup wall that cannot be clogged with mortar squeezings. Sure Cavity's mortar-blocking fabric ensures that the drainage channels stay clear and is permeable so that moisture can drain and the cavity can dry. A course of Sure Cavity angled at the bottom of the wall system provides an extra level of protection by holding mortar droppings away from the weeps and preventing mortar from bridging the cavity.

MTI’s Cavity Weep creates four weep holes every 9.5 inches and drains directly on the flashing, the lowest point of the wall system. Cavity Weep's translucent plastic blends with mortar for a superior appearance.

Rainscreen & Weeps Post Flood Retrofit

Brick mortar droppings plugged the bottom of this wall system, moisture cannot drain out. Excess mortar also “bridges” cavity and allows moisture to contact the sheathing, leading to rot, decay and mold.

Outdated construction practices created risky conditions for moisture damage and mold growth. Building professionals have noted that many of the homes affected by the 2016 & 2017 floods lack the necessary mechanisms to drain everyday moisture from walls.

The signs of moisture intrusion can remain hidden from the casual observer for years. Moisture intrusion into a wall system leads to a loss of structural integrity, rot, and mold. According to the Environmental Protection Agency, mold is a leading cause of allergies, asthma and other respiratory complaints.

The EPA advises that “the key to mold control is moisture control.”

Homeowners working to clean up after the flooding are encouraged to partner with a qualified contractor to discuss issues that affect the long-term health of the home and its occupants.

MTI is here to help.

Retrofitting a Brick Veneer Rainscreen

Plan A: Design a resilient building outside of the flood plain with a predictable rainscreen drainage plane so that when moisture enters a wall system it has a path to exit and will not come into contact with materials that could rot, mold, or deteriorate in the presence of moisture. MTI has hundreds of new construction wall details from common to complex in its HyperSpecs detail drawing library.

Plan B: Add those important moisture management features to an existing building. If the exterior of the structure has been removed many of the Hyperspecs detail drawings can be referenced when restoring the building. When the interior of a structure has been mucked out, and the cladding is visible from inside the restoration is possible using a detail like the one below.

Fixing It From the Inside - After Gutting a Flooded Home

In a brick veneer restoration from the interior, the goal is to protect the interior from moisture intrusion by adding the Sure Cavity™ rainscreen drainage plane. Weeps must be drilled in the bed joint mortar at the lowest point of the system to allow bulk moisture to exit the system and ventilate the cavity. Spray foam insulation can be used between the studs and the brick wall to restore some stability where the sheathing has been removed. Filling the remainder of the cavity with foam insulation (either spray foam insulation or rigid boardstock panels) increases R-value, protects the drywall from moisture and provides some additional structural strength.

Each restoration is unique, but this detail provides a place to start the conversation. To continue the conversation and design the best system for your own situation have your contractor email or call us.

FAQ - Frequently Asked Questions

Are There Other Considerations For Floor Recovery?
Where Can I Find Other Resources For Flood Recovery And Mold Removal?

Will This Prevent My Home From Flooding In The Future?

No. The rainscreen approach is a building science best practice to prevent entrapped moisture problems under normal conditions. Many brick veneers were constructed without the proper air gap behind the brick for drainage and ventilation. Without a rainscreen air gap normal weather conditions lead to a buildup of moisture in the wall system and structural deterioration as well as mold issues.

How Can I Reduce The Impact Of Future Flooding?

Using this rainscreen retrofit technique along with "wet floodproofing" approach for your interior renovation will result in a wall system that is drainable and dryable. Using flood hardy materials reduces the time and resources required to rebuild after a flood.

Do I Need To Plug Weep Holes During a Flood?

No. Unless your home is a submarine the exterior materials along with doors and windows are not watertight and will succumb to the flood waters. Standing water in contact with brick walls (or other veneers) will inevitably enter the structure and plugging weep holes will not improve the situation.

What Types of Insulation Can I Use?

Consider using insulation that is water tolerant, such as closed-cell insulation in spray foam or rigid foam panels. Closed-cell insulation will not absorb water and may not require removal in a future flooding event.